Study of Thermal Conductivity due to Spins in One-Dimensional Spin Systems AFeX3 (A=Rb, Cs; X=Cl, Br)

Large contributions of the thermal conductivity due to spins, κspin, in low-dimensional spin systems are expected to be utilized as highly thermal conducting materials. One-dimensional spin system RbFeCl3 with ferromagnetic chains and CsFeBr3 with antiferromagnetic chains in magnetic fields have been prepared in order to observe the contribution of κspin to the value of thermal conductivity. The temperature dependence of the thermal conductivity parallel to spin chains along the c-axis, κ//c, of RbFeCl3 enhanced around 3 K and 10 K by the application of magnetic field. In the thermal conductivity perpendicular to c-axis, κ⊥c, of RbFeCl3, on the other hand, it has been found that only one peak around 3 K is enhanced by the application of magnetic field. Since κ⊥c is mainly owing to the thermal conductivity due to phonons, κphonon, it has been concluded the peak of κ//c around 10 K in magnetic fields is due to the contribution of κspin. For CsFeBr3, it has been found that κ//c shows two peaks around 3 K and 25 K while κ⊥c shows one peak around 12 K in zero field. This indicates that there is a marked contribution of κspin to κ//c. κ⊥ However, the details of the marked contribution of κspin to κ//c are not yet clear, since κ//c has been suppressed by the application of magnetic field in contrast with the enhancement of the thermal conductivity in RbFeCl3.